Plasma Jet-Substrate Interaction in Low Pressure Plasma Spray-CVD Processes

Conventional equipment for plasma spraying can be adapted for operation at low pressure so that PECVD-like processing can be performed. The plasma jet generated by the torch is characterized by a high convective velocity and a high gas temperature. The influence of these properties on a deposition process are investigated in the framework of simple theoretical considerations and illustrated by various experimental results obtained with SiO x deposition. A conclusion of this study is that the deposition process is dominated by diffusion effects on the substrate surface: the deposition profiles and the deposition rates are determined by the precursor density and by the gas temperature on the substrate surface. The high velocity of the jet does not play a direct role in the deposition mechanism. On the other hand it strongly increases the precursor density available for the deposition since it efficiently transports the precursor up to the substrat

Two-fluid solutions for Langmuir probes in collisionless and isothermal plasma, over all space and bias potential

This paper presents solutions for the classical one-dimensional (1D radial and Cartesian) problem of Langmuir probes in a collisionless, isothermal plasma. The method is based on two-fluid equations derived from the first two moments of Vlasov's equation. In contrast to commonly used approximations, electron inertia and ion temperature are not neglected so that the fluid equations are symmetric in terms of electrons and ions. The fluid equations are reduced analytically so that the electric potential is the only remaining spatial function, which is numerically determined using Poisson's equation. The single radial solution applies continuously over the whole region from the probe up to the unperturbed plasma, in contrast to theories which separate the probe boundary region into a charged sheath and a quasi-neutral pre-sheath, and is valid for all values of probe bias potential. Current-voltage characteristics are computed for cylindrical and spherical probes, which exhibit non-saturation of the ion and electron currents. The 1D Cartesian case is also analysed, and the Bohm criterion is recovered only in the limit of large radius probes. Published by AIP Publishing

Current-Driven Magnetization Dynamics in Magnetic Multilayers

We develop a quantum analog of the classical spin-torque model for current-driven magnetic dynamics. The current-driven magnetic excitation at finite field becomes significantly incoherent. This excitation is described by an effective magnetic temperature rather than a coherent precession as in the spin-torque model. However, both the spin-torque and effective temperature approximations give qualitatively similar switching diagrams in the current-field coordinates, showing the need for detailed experiments to establish the proper physical model for current-driven dynamics.Comment: 5 pages, 2 figure

Analysis of resonant planar dissipative network antennas for rf inductively coupled plasma sources

The analysis of a radio-frequency (RF) planar antenna is presented for applications in plasma processing. The antenna is a network of elementary meshes composed of inductive and capacitive elements which exhibits a set of resonant modes. The high currents generated by RF power feeding under resonance are efficient for plasma generation. A general solution is derived for the currents in the driven dissipative network for these conditions. The dominantly real input impedance near antenna resonance avoids the high reactive currents and voltages in the matching box and RF power connections which can be a problem with conventional large-area capacitively and inductively coupled plasma sources. The driven antenna can be approximated by a parallel resonance equivalent circuit whose input impedance can conveniently be measured to interpret the dissipation due to the plasma

Generation of Whistler-Wave Heated Discharges with Planar Resonant rf Networks

Magnetized plasma discharges generated by a planar resonant rf network are investigated. A regime transition is observed above a magnetic field threshold, associated with rf waves propagating in the plasma and which present the characteristics of whistler waves. These wave heated regimes can be considered as analogous to conventional helicon discharges, but in planar geometry

Current-induced magnetization reversal in magnetic nanowires

The effect of pulsed currents on magnetization reversal were studied on single ferromagnetic nanowires of diameter about 80 nm and 6000 nm length. The magnetization reversal in these wires occurs with a jump of the magnetization at the switching field Hsw, which corresponds to unstable states of the magnetization. A pulsed current of about $\rm 10^7\, A/cm^2$ was injected at different values of the applied field close to Hsw. The injected current triggered the magnetization reversal at a value of the applied field distant from the switching field by as much as 20%. This effect of current-induced magnetization reversal is interpreted in terms of the action of the spin-polarized conduction electrons on the magnetization